Method and apparatus for airborne seismic exploration

ABSTRACT

In apparatus for seismic operation, a seismic energy source is constructed and arranged to be supported in a depending manner from a cable carried by a helicopter and is gradually lowered to rest on the earth&#39;&#39;s surface at each selected location while the helicopter hovers above. Means are provided for positively anchoring the seismic energy source to the earth&#39;&#39;s surface in order to impart a seismic input into the earth and is activated by remote control from the helicopter.

United States Patent 1 1 3,685,608 Hamilton 1451 Aug. 22,1972

[54] METHOD AND APPARATUS FOR OTHER PUBLICATIONS AIRBORNE SEISMICEXPLORATION Inventor: Ferris F. Hamilton, 320 High St.,

Denver, Colo. 80218 Filed: Nov. 3, 1969 Appl. No.: 871,167

Related US. Application Data Division of Ser. No. 738,572, June 20,1968, Pat. No. 3,509,960.

US. Cl ..l8l/.5 VM, 181/.5 EC Int. Cl. ..G0lv l/04 Field of Search..l81/0.5 VM, 0.5 EC

References Cited UNITED STATES PATENTS 9/1955 Bannister ..18l/0.5 Wade..18l/0.5

Williams, Sikorsky S-60 Flying Crane, American Helicopter, March 1959,pp. ll, 14

Primary Examiner-Benjamin A. Borchelt Assistant Examiner-N. MoskowitzAttorney-John E. Reilly 1 ABSTRACT In apparatus for seismic operation, aseismic energy source is constructed and arranged to be supported in adepending manner from a cable carried by a helicopter and is graduallylowered to rest on the earths surface at each selected location whilethe helicopter hovers above. Means are provided for positively anchoringthe seismic energy source to the earths surface in order to impart aseismic input into the earth and is activated by remote control from thehelicopter.

8 Clains, 5 Drawing Figures METHOD AND APPARATUS FOR AIRBORNE SEISMICEXPLORATION This is a division of application Ser. No. 738,572, filedJune 20, 1968, now US. Pat. No. 3,509,960.

This invention relates to a novel and improved apparatus for seismicexploration utilizing helicopters or like aircraft and a surface typeseismic energy source which is supported and controlled from theaircraft for an essentially continuous airborne seismic operation.

In the past, seismic exploration has generally been conducted with landvehicles which transport the seismic equipment such as the seismicenergy source, geophones and recorders to a location. Seismic sourcespresently in use are of a variety of types including explosives,hydraulic and electromagnetic vibrators, or weight drops. In each case,when the seismic source is activated to generate seismic waves, thereflected waves are detected by the geophones, the mechanical energyconverted into electrical energy, and recorded by a recorder system. Theequipment is then moved or transported to each next location insuccession.

A particular difficulty in using land vehicles is in transporting theheavier seismic equipment into and between inaccessible locations, suchas, swamps or forest areas; and while some attempt has been made in thepast to employ aircraft in seismic explorations, for the most part thishas been restricted to moving the pick-up and recording instruments toeach location for detecting the seismic waves or moving portable seismicdrills, because of the extreme weight of the seismic input equipment.

Thus an important factor in transporting and placing a seismic energyinput source on the earths surface by helicopter or other aircraft isthat the equipment and ancillary equipment must be comparatively lightin weight; yet, to be effective in use the source must direct its energyinto the earth without the heavy weight or load customarily employedeither as a part of or in direct association with the energy source.

Accordingly, it is an object of this invention to provide a simple andefficient apparatus for airborne seismic exploration wherein alightweight energy source can be anchored to the earths surface forrelease of its energy into the earth with maximum coupling, is quicklyreleasable and rapidly transportable between locations.

Another object of this invention is to provide a new and improvedapparatus for fully airborne seismic exploration which is capable ofreaching otherwise inaccessible locations.

It is still a further object of this invention to provide an airbornesurface contact energy seismic source particularly suitable for use incombination with a helicopter and of being activated by remote controland wherein reduction in weight of the energy source is compensated forby positively but releasably anchoring the source to the earths surfaceat each selected location.

In accordance with the present invention there is provided a novel andimproved seismic exploration apparatus which includes suspension of thesurface contact, seismic energy source by cable means preferably from ahelicopter. Helicopters are particularly suitable because of theirability to hover above each location as well as to provide electricpower supply and other remote control capabilities. Following suspensionthe source assembly is lowered by the craft into contact with theearthsurface either by decreasing the craft elevation or by raising andlowering a cable from which the source is suspended by operation of awinch in the craft. The source assembly is then secured to the earthssurface by driving an anchor member downwardly from the assembly intothe earth and in such a way as to draw the surface-contacting portion ofthe assembly against the earths surface. The seismic input source isthen activated preferably by remote control from the helicopter togenerate a seismic surface input while the helicopter is hovering abovethe location. After each seismic generation the anchor member isretracted from the earths surface and the assembly lifted and carried toanother location by the craft where the procedure is repeated.

Other objects, advantages and capabilities of the present invention willbecome more apparent as the following description proceeds taken inconjunction with the drawings, in which:

FIG. 1 is a generally schematic elevation view depicting the surfacecontact seismic source assembly being carried by a helicopter to aparticular location and lowered to the ground and a preferred form ofretractable anchor for the assembly is shown in dotted form in itsextended position.

FIG. 2 is a generally schematic elevation view depicting the assembly inthe anchored position with the supporting helicopter hovering above andthe activation of the seismic energy source to generate waves which arepicked up by conventional pick-up and recorder devices.

FIG. 3 is a generally schematic elevation view of the assembly after theanchor has been retracted from the earth as a preliminary to lifting bythe helicopter to a next succeeding location.

FIG. 4 is an elevation view partially in section of the surface contactanchor assembly shown in FIGS. 1, 2 and 3; and

FIG. 5 is a top plan view of the assembly shown in FIG. 4.

Referring now to the drawings in FIGS. 1 to 3, there is schematicallyshown a seismic exploration system embodying the features of the presentinvention which will first be described generally followed by a moredetailed description, and as shown includes an aircraft 1 l which in thepreferred form is a helicopter having a seismic source assembly 12suspended therefrom by a cable 13. The seismic source assembly 12 may beflown to each location by the helicopter and then suspended from thecable as shown and lowered toward the earth; or the assembly may firstbe attached to the end of the cable while resting on the ground, raisedto an elevated position and flown to the next location in a dependingtowed manner. A motor driven winch 14 may be provided in the craft 11for raising and lowering the assembly 12 from the aircraft and anelectric power source and control box represented at 15 is located inthe aircraft. There are currently available a variety of helicoptershaving a suitable electric power source capability such as the 204-Bhelicopter CFCBK which will provide electric power for use with controlswitches in the aircraft remote from the seismic source assembly 12. Theassembly may thus be lowered from the aircraft by elevating or loweringthe aircraft or by controlling the motor driven winch 14, although theformer is preferred.

After the helicopter 1 1 has reached the particular location it willhover above the location and the assembly 12 is gradually lowered froman elevated position to a ground contact position on the earths surfacedesignated 16. An anchor member 17 to be hereinafter described in detailis preferably mounted on the assembly 12 and is driven downwardly intothe earth to an extended earth-penetrating position, as is generallydepicted in dash lines 18 in FIG. 1, while the helicopter is hoveringabove and its stroke is controlled in such a way as to positively drawthe assembly 12 down against the earth in a manner described more fullyhereinafter. A seismic source, hereafter described more fully, ismounted on the assembly and is activated to generate a seismic inputinto the earth. As depicted by dash lines 22 in FIG. 2, the seismicwaves generated and transmitted into the earth are reflected from thelower subsurface structure 23 to one or more pick-up devices 24 andrecorders 25 in the usual manner. The recorder and pick-up devices maybe transported to the location in a conventional manner, such as by aland vehicle, but in the preferred airborne operation of the presentinvention also may be transported to each location by helicopter.

After the seismic source has been activated and the testing completed,the anchor 17 is retracted, as shown in FIG. 3, followed by lifting theseismic input assembly and flying it by helicopter to the next locationwhere the same sequence is carried out in conducting another seismictest.

Referring now to FIGS. 4 and 5, the surface contact seismic sourceassembly as shown is comprised of a generally flat base or lowerplatform member 31 having a substantially flat undersurface and havingthe retractable anchor 17 which is in the shape of a spear or stake andis shown as being constructed of a generally cylindrical tube or hollowshaft having a solid pointed portion 30a at its lower end arranged fordownward extension through a guide sleeve or bushing 32 located in theplatform. The shaft is supported from the platform for movement from araised position as shown in FIG. 1 downwardly into the earth to a fullyextended position as shown in dash lines at 18 in FIGS. 1 and 4. Theshaft 30 is attached at its upper end to the undersurface of an upperhorizontal support plate 33 with a pair of drive members extendingparallel to and on opposite sides of the shaft 30 between the lowerplatform 31 and the upper plate 33. Each drive member includes adouble-acting cylinder 34 and a piston 35 which reciprocates in thecylinder to raise and lower the anchor shaft 30. For the purpose ofillustration, where hydraulically operated cylinder units are provided,pressure and return lines 37 are connected to opposite ends of the drivecylinders 34 and lead from a regulated source of supply which may besuitably defined by a pump P, reservoir or tank T, motive source M forthe pump, and a pilot operated valve V to control the flow of fluid toand from opposite ends of the cylinders 34. Here the valve V togetherwith the power source M may be controlled either from the aircraft orfrom the ground as desired.

A central drive member is located within hollow shaft 30 for controllingthe pivotal movement of blades 29 and includes an upper cylinder 41 andplunger 42 for selectively actuating the finger members 29 at the lowerend of the shaft 30. The members 29 are hinged at their lower ends onopposite sides of the shaft 30 for laterally outward pivotal movementfrom the body and, to this end, pivotally interconnected links 43 extendfrom a central portion of each member 29 to the bottom of the plunger 42in order to pivot the legs outwardly and inwardly. The latter may bedone in response to reciprocal movement of the plunger under the controlof pressure and return lines 37 leading from a second control valve V.When the shaft 30 is driven into the ground by retraction of the pistonrods 35 through their cylinders 34, the finger members 29 are held flatagainst the outer surface of the shaft 30. After substantial penetrationto the extended position, shown dotted in FIG. 1, the shaft is raisedslightly to the position shown and simultaneously the fingers 29 arepivoted to the position shown in FIG. 4 thereby drawing the base 31downwardly against the earths surface.

The seismic source is preferably defined by a pair of vibrators 44disposed at opposite ends of the base 31 and each contains anelectromagnetic or hydraulically operated driving member 45 to generatevibrational impulses which are transmitted into the earth. A line 46 isshown leading to each of the members 45 and also may extend to otherrequired apparatus on the base to be controlled remotely from thehelicopter, depending on the type of seismic source being employed. Thelower extremities of the suspension cable 13 are attached to the top ofthe upper platform 33 using lugs 47 at each corner thereof, and thecable 13 extends upwardly to the helicopter to suspend the entiresurface contact assembly from the helicopter in a balanced manner.

In the detailed operation and sequence, after the assembly 12 has beenlowered by the aircraft 1 1 to rest at location 16 (FIG. 1) it is thenpositively anchored to the earth. This is accomplished by firstactuating cylinders 34 which retract the associated pistons 35 to drawplate 33 downwardly toward platform 31 and at the same time shaft 30 ispositively driven downwardly into the earth to a preselected lowermostposition indicated at 18. Cylinders 34 are then actuated through theirregulated source to provide a reverse flow in the cylinder to push thepistons out of the cylinders and thereby raise shaft 30 and at the sametime cylinder 41 is actuated to drive its piston 42 downwardly to spreadblades 29 so that blades 29 are moved laterally of the shaft 30 to anextended position inclined at an angle to the horizontal, and thisaction pulls the base 31 against the earths surface. Upon anchoring thebase as described, the seismic source 45 is energized to generate theseismic input.

To release the anchor 17 cylinders 34 are again actuated and theirpistons 35 are retracted into the cylinder to drive shaft 30 downwardlyand at the same time cylinder 41 is actuated to retract its piston 42 topivot the blades inwardly to their original position in close proximityto shaft 30. Fluid pressure to the cylinders 34 is reversed to force thepistons 35 outwardly thereby causing the shaft 30 to be removed from theground to the upper retracted position while cylinder 41 and piston 42act to hold the blades 29 in the retracted position. After shaft 30 hasbeen fully retracted (FIG. 3)

the assembly 12 is ready to be elevated and carried by the aircraft tothe next location. In a conventional and well-known manner the pick-ups24 and recorders 25 are transported, preferably by helicopter lift, toeach new location.

While various means can be employed to control activation both of theseismic source and of the anchor, one preferred way is to provide anelectrically actuated type such as electric solenoid operated valves onthe base 31 which may be supplied with electric power through anelectrical cable extending upwardly with the support cable to thecontrol box in the helicopter so that personnel in the helicopter maycontrol the activation of the seismic source. In a similar fashion, theanchor may be controlled from the helicopter. As a suitable alternativeto the conductive lines in the cable 13, a radio control in thehelicopter may be used. The drive for the anchor may also be of avariety of types including a linear electric motor actuated by theelectric source in the helicopter.

Although the seismic source has been illustrated somewhat generally anda hydraulic or electromagnetic vibrator has been referred to as onepreferred form it is understood that it may be of a variety of seismicsources such as an explosive type or other forms of known mechanicalvibrators. Further a weight drop may also be employed on an assemblywhich supports the weight above the earth and which may be activated orreleased from a control in the aircraft. A variety of earth anchors arealso suitable for positively drawing the platform against the earth,such as, for example, an auger.

Although the present invention has been described with a certain degreeof particularity, it is understood that the present disclosure has beenmade only by way of example and that changes in details of structure andsystem components may be made without departing from the spirit andscope thereof.

What is claimed is:

1. Surface contact seismic energy source apparatus adapted for airbornecarriage and placement on the earths surface for seismic explorationcomprising a base having an undersurface adapted for contacting theearths surface, airborne means for gradually lowering the base intocontact with the earth, a releasable anchor member supported on the basefor reciprocal movement from a raised position to a position downwardlyof said base into the earth for anchoring said base to the earth, saidanchor member having means movable outwardly into the earth forpositively drawing the base down against the earth after the anchor hasdriven into the earth to its fully extended position, means for drivingsaid anchor member into the earth, a seismic energy source on the basefor generating seismic waves in the earth, and means for selectivelycontrolling the actuation of the anchor member and seismic energysource.

2. Surface contact seismic energy source apparatus as set forth in claim1 wherein said anchor member includes a shaft portion mounted forvertical downwardly directed movement into the earth.

3. Surface contact seismic energy source apparatus as set forth in claim2 wherein said anchor member include a pair of oppositely disposedblade-like members portion into an angularly inclined earth-penetratingposition.

4. Surface contact seismic energy source apparatus as set forth in claim3 wherein said blade-like members are pivoted outwardly and inwardly ofthe shaft portion independently of the reciprocal movement of said shaftportion.

5. A system for airborne seismic exploration comprising a weighted,surface-contacting, seismic energy source assembly, an anchor memberincluding releasable anchoring means movable outwardly into the earthfor releasably anchoring the assembly to the earth s surface by drawingthe assembly against the earths surface after the anchor has been driveninto the earth to its fully extended position, aircraft means having acable suspended therefrom for supporting the assembly in a dependingmanner to lower said energy source to a position at rest on the earthssurface, activating means for activating said energy source assembly togenerate a seismic energy surface input into the earth at the desiredlocation by activating said assembly, and release means for selectivelyreleasing the anchor including said releasable anchoring means from theearth.

6. A system as set forth in claim 5 wherein said cable means includeselectric conductive lines for controlling the activating means remotefrom the surface contact assembly.

7. A system as set forth in claim 5 wherein said cable includes awinding apparatus in the aircraft for lowering and raising the cablemeans and attached surface contact apparatus from the aircraft means.

8. A system as set forth in claim 5 wherein said aircraft means is ahelicopter.

1. Surface contact seismic energy source apparatus adapted for airborne carriage and placement on the earth''s surface for seismic exploration comprising a base having an undersurface adapted for contacting the earth''s surface, airborne means for gradually lowering the base into contact with the earth, a releasable anchor member supported on the base for reciprocal movement from a raised position to a position downwardly of said base into the earth for anchoring said base to the earth, said anchor member having means movable outwardly into the earth for positively drawing the base down against the earth after the anchor has driven into the earth to its fully extended position, means for driving said anchor member into the earth, a seismic energy source on the base for generating seismic waves in the earth, and means for selectively controlling the actuation of the anchor member and seismic energy source.
 2. Surface contact seismic energy source apparatus as set forth in claim 1 wherein said anchor member includes a shaft portion mounted for vertical downwardly directed movement into the earth.
 3. Surface contact seismic energy source apparatus as set forth in claim 2 wherein said anchor member include a pair of oppositely disposed blade-like members hinged along a lower portion of the shaft portion so as to pivot outwardly in a lateral direction from the shaft portion into an angularly inclined earth-penetrating position.
 4. Surface contact seismic energy source apparatus as set forth in claim 3 wherein said blade-like members are pivoted outwardly and inwardly of the shaft portion independently of the reciprocal movement of said shaft portion.
 5. A system for airborne seismic exploration comprising a weighted, surface-contacting, seismic energy source assembly, an anchor member including releasable anchoring means movable outwardly into the earth for releasably anchoring the assembly to the earth''s surface by drawing the assembly against the earth''s surface after the anchor has been driven into the earth to its fully extended position, aircraft means having a cable suspended therefrom for supporting the assembly in a depending manner to lower said energy source to a position at rest on the earth''s surface, activating means for activating said energy source assembly to generate a seismic energy surface input into the earth at the desired location by activating said assembly, and release means for selectively releasing the anchor including said releasable anchoring means from the earth.
 6. A system as set forth in claim 5 wherein said cable means includes electric conductive lines for controlling the activating means remote from the surface contact assembly.
 7. A system as set forth in claim 5 wherein said cable includes a winding apparatus in the aircraft for lowering and raising the cable means and attached surface contact apparatus from the aircraft means.
 8. A system as set forth in claim 5 wherein said aircraft means is a helicopter. 